Concrete foem material



Dec-.'12, 1944.

R. D. BEI-1Mv CONCRETE FORM MATERIAL Filed Oct. 28, 1941 Patented Dec.12, 1944 CONCRETE roam Richard D. Behm, Vancouver, Wash., assignor toMaud M Wood Working Company, Greg., a corporation of Oregon Portland,

l Application October 28, 1941, Serial No. 416,854 (ci. :e-431i l 2Claims.

The present invention relates to concrete forms,

and more particularly to materials to be used in p the construction ofsuch forms.

of the concrete yi'sfree from craters and surface cavities. The globulesof water which are the causeof craters andsurface cavities are elim-Concrete usually is poured in a semi-fluid state t into forms in whichit sets and hardens, after which the formsa're removed land the concreteallowed to cure. The forms usually are constructed of lumberwhich issecured inplace and braced by an outer framework of timbers. Upon theremoval of forms of the usual construction. the surface of the concretewhich was'in contact with the inner surface of the form is not smooth.

but is pitted with a great number of small craters or cavities formed bybubbles of air and water which were present in the mix before it set. 1The problem has been to eliminate these craters and cavities, whichcommonly occur in all concrete surfaces. In exterior walls waterseepsinto the surface cavities and, upon freezing, causes furtherdisruption of thesurface and exposes additional cavities, tendingtowardv a shortened life of the structure. In-ordinary commercialconstruction, in order to improve the appearance and also the weatheringstrength of wall. itis common practice to provide afstucco coating`whiclnhowever, adds appreciablylto the. costl of the finished structure.lOn dams, spillways, and

similar projects. the surface openingspmustbe.

filled, since onv such projects. if tha'concrete is not properlyfinished, it is sublect'lto considerable wear.

. 4 When the concretemixture is made itisnecessary to add water insufficient quantityfsojthat the masswill be fluid enough topourand-ow toall parts of the form. The cementi'n vthe concrete combines with onlyapart'of the Water.`

The remainder of the waterfis present only to give the mass fluidity.This water is necessary only vto facilitate mechanical 4handling of theconcrete. Concrete undergoes ian initialsetwaterfrom the layer of inatedby absorption intothe absorbent lining. Furthermore, it-has been foundthat the surface of the concrete is appreciably harder and stronger thanwhen it is poured'against a nonabsorbent surface. This is of great valuebecause it improves tremendously the wearing surface of the concretestructure.

In accordance with one form of the invention, a l

base member such asa sheet of i plywood is provided on one surface witha layer of `highly moisture absorptive material. Concrete forms arebuilt of this material with ther absorptive layer ron the inside of' theform, which layerrapdly withdraws the free water out ofv the Vmixture,filters the cement from the watergand leavesfa remarkably smooth, hardsurface after the cement has set. Accordingly,l the surface lof concretestructures made with forms of this material is smooth and of unusualdensity, vand of` great mechanical strength. c

'It is an object of the present invention, Vtherefore. to provide a newland improved material `for making concrete forms which will produce asur- -face on the concrete structure substantially smooth and free ofnnfacelrregularities.

More-especially, it` is an` object of the invention-fto providers. `newand improved material for making concrte forms which will absorb freeconcrete next adjacent thereto, leavin: the concrete surface substam 3tially smooth and without surface cavities.

1t is a further `obiectof the invention to provide a new and improvedlaminated material for making concrete 4forms which' will produce4 ating reaction 'within a reiatlvelysnort .time nur f it is poured-atwhich time the excess'water, i. e.;

that portion. ofthe water lwhich. does not com- -bine with the cementisgivenlv up and 'accumuparticularly at the surface'of' lates as-alcbulesl` the form. When the usual type of woodenfrms is used. thisexcess water will be observed to-dr'ain out through the cracksb'ctweenfadjacent boards, or eventually be absorbed into the wooditself,

leaving small craters or cavitiesfin the surfaces of the concrete.

Applicant has discovered that if the form is lined with an absorbentmaterial and the concrete is poured against this absorbent surface,then, when the form is stripped away. the surface surface on theconcrete which is of hi'ghmechanical strength and extremely .weatherresistant. 1 Itis a further object of the invention to irro-l 'vide anilnprorved-4 material for makina concrete 'forms whichis productive ofagconcrete etnic- `mns apprelamy harder and stresser con- -ilivwhicnpossesses est,

. face havin! crete" poured in! heretoforefin use, and

a-high degree of strength and' hard- A'Witii other and f advantages invmind,-

invention resides' in the structure hereinafter described andillustrated in 'thedrawl vins, 'afueras'. understood that various*sinuses` in form. proportion and `detailsy of Iconstruction within thelscope of the appended claims may be resorted to without departing fromthe spirit or tlyfimprovod wearingsurtion.

In the drawing: A f

l L sacrificing any of the advantages' of the inven Figure 1 is a crosssectional view through a secl tion of a concrete wall being constructedwith 5 the aid of forms made of material, according to` the presentinvention. Y

Figure 2 is a fragmentary view in perspective of concrete form materialembodying the invention, portions vthereof be broken -awa'yfvfor l0greater clarity., l Figure 3 is a perspective view of a portion of a.concrete form making material Vshowing -a modification of the structureillustrated in Figure 1.

Figure 4 is a cross sectionarview of a concrete l wall being constructedin accordance with-aA cus- L and which is explanatory'` l of the objectsof the present invention. Figure 5 is a fragmentary 'sectional elevation2o of a Iconcrete form making materialy according to a modification ofthe invention.

tomary procedure,

- Inorder to impart a dense lsmooth 'surface tc the concrete, itisnecessary, as'aflrst considera- 1 tion. that the wet mix contain''suchan excess 25 of .lwa'ter I that the'mlx, whenpouredr will ow e f lreadilyto allapa'rt's-of'the form, 'leaving s'ubstantially no voids :orair pockets therein.l However, this excess wateris somewhat' detrimentalto the y l strength of the mass whenit is finally set, and the 30 excessor ,freewater' should be removed from at least the layer of concretenext adjacent the form within the short period of time after the mix ispoured andbefore setting takes place. In the 3structurel-embodyingtheinvention; the excess 35 Y water iseffectively removed by theprovisionAof extremely-'fine drainage apertures in a readily -wettable materialatthe' surface/'of' the form so gthatwater will pass quicklytherethrough without l carrying any cement with it.` -l This absorbent40 material at the surface ofthe form acts as a lter so that no cementis lost from the mix. When the wetconcrete o'wsinto contact with theabsorbent v lining of the form, the lining immediately absorbs free'water into itself, as well as any air bubbles which have. becomeoccluded in the mixture, and leaves a, remarkably smooth and. hard.surface after jthe! cementv has set..4 `By thus absorbing awayzsonie -ofthefree water, the absorbent form lining increases the strength of theconcrete ad- 50 jacent the'surface; and it is at thesurface of thelstructure that increased strength and hard- 'ness .arel most useful,both from the standpoint .of structural strength and of'wearing quality.l l In', accordance with the present invention, I

provide Aconcrete formmakng material comprising a vrelatively rigid baseunit Asuch as, for example, a -sheet of plywood having a plurality ofpliesof wood veneer adhesively secured interfacially, and inwhich thegrain of each ply is ed disposed across' the grains of adjacent plies.To

one side of the base ,member is secured a relatively i thin sheetofmoisture absorptive material. Referring to the'drawing,v the form forthe concrete wall I0 is formed bya pair of spaced sheets of form makingmaterial, each consisting of a base portion l2 which,v in thisinstance'is a three- `ply plywood panel having suitably secured to oneside' thereof layers I3 of moisture absorptive nia- The number of Vpliesfor the laminated 70 terial. base portion-l2 will, of course, dependupon the .necessary mechanical strength required of the form, takinginto considerationjthe spacingof the frameworktimbers, thethickness of.the wallgto bebuilt,l and other factors. Infthe modification 7s occurs.

face of thevabsorptive liningbe of ne texture so 'as to substantiallyfilter'cement from the water f being absorbed thereby. `This lteredlayerof l cement next adjacent the form provides an exl tremely hard,4 layerover the outer surface of the in Figure 3 the base portion I2 lcomprisesa vev ply plywood panel, though it will be' obvious that the number ofplies and hence the thickness of the base portion may be varied asdesired.

The lining yi3 may be of any absorptive material, it being preferred,however, that the outer surface thereof be substantially smooth, thatis, having few ifv any fibers extending outwardly therefrom which mightbecome imbedded in the cement and interfere with the clean Aremoval ofthe form lfrom the structure after the concrete has hardened. Onematerial which has been found suitable foruse as an absorbent lining is`a felted material made of scrap paper and ground wood,-commonly knownas chip board. It is preferredfthat the surface of the felt becalendered toproduce a substantially smooth and close textured surface,although it may be desirable to use material having textured finishes onthe absorbent lining which would be transferred to the lsurface of thecompleted structure.

A high degree of absorptivenessis required to produce the best -vresults.; However,r the surface. against which the concrete ispouredshould not be verygreatly compressible for the reason that the yconcrete is `pouredaga'instthis surface",with considerable forcev anddents might otherwise be made by rocks con'tainedin the concrete which ywould' destroyA the smoothness of the lconcrete.

after it has set.AV For'this reason the"thickness y of the absorptivelining shouldbe 'of thev order of 4one-eighth to one-fourth inch, ithaving been determined that a llining of this thickness mounted upon arigid base portion is only slightly compressible even-though watersoaked. An aby sorptive liningof such material and of such thicknesswill rapidly absorb free water from the layer of wetconcrete nextadjacent thereto to V'avdepth l `of about one-half-'inchl'k Thisabsorptiontalles l place within thev first few 'secondsafterthe'vconcrete-has been poured', -and thev water which' has beenabsorbed intoithe Vlining will rapidly be 'replaced by-Iiuid concretebefore the setting action `It-is important that the'outermost surnishedwall. -Tests vshowv that -the concrete 1 hardened with an absorbentlining sulchA as herel in-disclosed is appreciablystronger than concretepoured into forms of ordinary construction; and is more resistant todeterioration by freezing.

The absorptive lining I 3 is preferably adhesively secured to theplywood vbase panel I2,v and the adhesive employed .to secure the liningshould permit the transfer of Water from the absorptive llining to the vbase member. The adhesive coating betweentheplywood base l2' and theabsorptive lining i3 is indicated at. I4 in AFigure 2, and prefierablymay consist -of a solution of silicate of soda, commonly knownas waterglass. Afterl the original absorption of mo' ture from the wet-mix 5, bythe absorptive liningl, the moisture from the lining is `graduallytransferredthrough the glue line to the wooden'base member I2,v and theabsorptive lining is renderedA capablev of absorbing additional waterliberated during the second stage of the chemical change lin theconcrete.

It will be appreciated that in the structure embodying the presentinvention, eachfof 'the'laminations is coextensive with each' of theother laminations inthe structure, and that,v duel tothe relativelylargesizeof the panelsused in makmay to some extent escape from'such forms atthe joints between adjacent pieces of shiplap, but none of the cement isltered from the water, and it is not uncommon to find the lapped edgesof such form material filled with cement after the concrete hashardened. Also illustrated in Figure 4 is 'the manner in which Waterpockets are formed in the surface of the concrete wall. There isillustrated globules of water I5 lying in contact with the wooden formsI6. yEventually this water is absorbed into the wood, but not untilafter the initial setting action has taken place. The escape of thewater globules I5 leaves cavities and craters in the surface of theconcrete wall and beneath these exposed cavities are additional cellularcavities I1 formed by water globules formed at the time the concrete waspoured and from which the water has since evaporated from the wall.During the winter seasons the outer cavities becomes filled with Water,which, upon freezing, disrupts the surface and exposes cavities lyingtherebeneath, thus materially shortening the life of the structure.

In Figure 5 is illustrated a laminated concrete form material comprisinga relatively rigid basel unit of corrugated iron I8, to one side ofwhich is secured a sheet of moisture absorptive material I9. Thislmodification is particularly useful when it is desired to impart afiuted surface to the finished wall structure.

, After the concrete has hardened to the desired degree, the forms mayreadily be stripped therefrom, the absorptive lining being substantiallynon-adherent to the concrete surface. By the use of the concrete formmaterial herein described, the finished wall will be substantially freeof surface depressions or cavities such as heretofore have been causedby water pockets. The

entire surface of the nished Wall will be covered with an extremelydense layer of cement which was filtered from the water absorbed by theabsorptive lining, and the wall structure to a depth of the order ofone-halfinch or more will be substantially free of voids, thus producingexceptionally high mechanical strength resulting from a conditionanalogous to case hardening. Moreover, the surface of the wall producedby forms constructed in the manner described possesses a smoothnessequivalent to that of a trowelled plaster surface and may be tinted orpainted as desired.

Having now described my invention and., in what manner the same may beused, what I claim as new and desire to protect by Letters Patent is:

1. A concrete form member consisting of a plywood base member having anabsorptive plurality of plies of wood veneer adhesively securedinterfacially, and a single lamination of relatively thin highlyabsorptive material secured to one surface of said plywood base member,a layer of moisture permeable, Water insoluble adhesive securing saidabsorptive material to said base member throughout the areas of thecontacting faces thereof each of said laminations of said material beingcoextensive with eachV of the other of said laminations, said absorptivematerial being placed to engage the surface of concrete poured into saidform for absorbing water directly therefrom.

2. A concrete form member consisting of an absorptive plywood basemember having a. plurality of plies of wood veneer adhesively securedinterfacially, and a single lamination of relatively thin, highlyabsorptive material secured to one surface of said plywood base memberand placed to engage the surface of concrete poured into the form forabsorbing moisture directly therefrom, said base and lamination ofabsorptive material being secured together by a layer 4of moisturepermeable, Water insoluble adhesive which secures said absorptivematerial to said base membervthroughout the area of the contacting facesthereof, said thin layer of material and the base being coextensive witheach other and the thin layer being provided with a calendered surfacehaving extremely ne apertures therethrough for filtering cement fromwater absorbed by said material.

RICHARD D. BEHM.

